How to find x,y,z coordinates of a mesh in edit-mode?
As ideasman42 wrote in his comment, this will work for any mesh in edit mode, regardless of whether it was imported from PLY or any other format, or generated within Blender:

import bpy, bmesh

bm = bmesh.from_edit_mesh( bpy.context.object.data )
mw = bpy.context.object.matrix_world 

selected_verts_coordinates = [ mw * v.co for v in bm.verts if v.select ]

print( selected_verts_coordinates )


This will only work for selected vertices when the mesh is in edit mode.